Plastic coated embossing roll and method



United States Patent Office 3,364,051 Patented Jan. 16, 1968 3,364,051PLASTIC COATED EMBOSSIN'G ROLL AND METHOD Frank W. Broderick, P0. Box 2,Stirling, NJ. 07980 No Drawing. Filed Feb. 19, 1965, Ser. No. 434,100 4Claims. (Ci. 117--8) This invention relates to a plastic coated roll forembossing a roll of foil or foil laminate and more particularly to apair of mated embossing rolls one of which is plastic coated.

In the past, rotary register embossing of foil laminates and paper hasbeen accomplished in line by (a) rotary printing stations using engravedmatched hardened forged steel rolls mated with herringbone gears, (b) byuse of a female engraved steel chrome plated roll mated to a vinylcoated. roll thru suitable gears followed by a curing process and (c) byuse of a female engraved steel chrome plated roll in conjunction with afree running rubber or polyurethane plastic roll. Not one of thesemethods is entirely satisfactory.

The (a) or matched hardened forged steel roll combination is veryexpensive, requires considerable time and skill to set up in a press andcauses tears and web breaks with the slightest misalignment.

The (b) or vinyl coated and steel roll combination presentsdisadvantages due to the difiiculty of maintaining uniform curingtemperatures across the entire roll face of the vinyl coating during thecuring and mating procedure. Harmful variations of the curingtemperature range are created by the metal masses in the journal insertsand by the conductivity loss of temperature thru journal and framecontacts. Such losses are fatal to uniform curing of vinyl coatings andthus limit the use of this (b) combination to large patterns, preferablylocated at least 6 inches from the ends of each roll. Moreover, caremust be taken with vinyl rolls during cleaning operations since thevinyl coating is soluble in many of the solvents commonly used to cleanembossing rolls.

The (c) or free running rubber or polyurethane plastic combinationpresents difficulties which yield poor embossing or bursting of the webwhen pressure for deep embossing is applied. This condition is createdby the condition that the greater the pressure exerted by the steel rollagainst the rubber or polyurethane back-up roll the greater is thedeformation of the back-up roll so that the peripheral speed of the webincreases above normal web tension speed immediately before, after andthru the direct point of tangency of pressure contact. Actually, thebackup roll material in contact with the web is moving faster in theseareas than either the web or the balance of the covering of the back-uproll, such speed up movement being generated by compression of theengraved roll thru the web to the back-up roll, resulting in increasedperipheral speed and decreased gap due to rotative distortion of theback-up roll. The result of this unbalance between engraved steel rolland the free running back-up roll distorts and breaks the web especiallyin those areas where the engraved roll and free running rubber orpolyurethane roll require heavier pressure due to their use as pull ortension control rolls.

It is an object of this invention to produce a plastic coated maleback-up embossing roll having none of the defects of the prior art.

It is another object to provide a back-up roll having a compressiblepaper pulp base coated with a plastic coating of suitable thinness.

These and other objects of this invention will become apparent uponreading the following descriptive disclosure.

A conventional steel roll is engraved in the conventional manner eitherby photo engraving or machine engraving after which it may be hardenedorchrome plated in the conventional manner. This roll may be a male or afemale roll. For example, a female roll having a diameter of 10.000inches is provided. A mating male roll is then prepared having anoutside diameter .030 inch less than the female roll of 10.000 inches.The outside diameter of the male roll therefore is 9.970 inches. To this'male roll of 9.970 inches there is laminated a loose pulp board of .024inch in thickness. While board lamination is preferred, any compositionsuch as plastic, cardboard or other material which may be laminated tothe male metal roll may be used providing it is compressive underpressure. After the pulp has been securely laminated to the metal rollit is dampened with a solvent; in the case of cardboard with Water; inthe case of vinyls with methyl ethyl ketone, etc., and it is then gearedto the female roll and rotated under pressure until the pitch diameterof the roll is compressed to 9.995 inches. That portion of the damppaper pulp which is forced into the female cavities will not compressmaterially and the outside diameter of this portion of the male rollwill be 10.018 inches. This outside diameter dimension is taken at thetop of the protuberances and the pitch diameter is taken at the bottomof the protuberances. At this stage the rolls will emboss foil laminatebut the male roll could be easily damaged by splices, creases andsimilar imperfections passing between them. Therefore to the compressedpulp male roll surface there is added polyurethane by means of spray orother conventional manner to a thickness approximately 50% greater thanthe foil laminate material to be run. For example, when a .003 inchthick paper and foil combination is used, then the polyurethane coatingwould be approximately .0045 inch thick.

This coating is now cured to the previously laminated and mated pulppaper by curing for several hours at about 270 F. The time andtemperature of curing varies greatly with the addition of differentplasticizers to the spray. After curing the rolls are rotated togetherin such a rnanner that the soft pulp protuberances compress with thepolyurethane to a height of .012 inch and the pitch diameter increasesto 10.000 inches giving a perfectly mated set of rolls, the top rollbeing steel and either hardened or chrome plated and the bottom rollbeing metal laminated with pulp to preserve the pattern and coated withpolyurethane to resist web breakage and bursting and damages due tocreases, splices and solvents.

According to this invention a suitably thin layer of resilient plasticis bonded to a laminate layer of a nonmetallic composition. Thepreferred plastic layer is of polyurethane but other plasticcompositions: are operable.

This invention has been described by means of an illustrative embodimentthereof but clearly it is of broader scope.

I-claim:

1. The method of preparing a back-up roll to prevent damage thereto andadapted to mate with a female embossing metal roll comprising laminatinga resilient composition board to a steel roll of suitably smalleroutside diameter to produce an overall diameter slightly less than thepitch diameter of said female embossing roll, moistening saidcomposition board with a suitable solvent, rotating said moistened rollin contact with said female roll to obtain a pitch diameter of the maleroll a few thousandths of an inch less than that of the female roll,adding a thin layer of flexible plastic to said composition board,curing said plastic layer at a suitable temperature for a suitable timeto produce a male backup roll having the pitch diameter of the femaleroll.

2. The method of claim 1 wherein a polyurethane layer of plastic isadded by spraying a solution thereof.

3 4 3. The method of claim 1 wherein a polyurethane layer ReferencesCited of plastic is added by dipping a solution thereof. UNITED STATESPA 4. The method of claim 2 wherein the thickness of the 805 699 11/1905Avril sprayed polyurethane layer is fifty to one hundred percent greaterthan the sheet material to be run between the embossing rolls.

5 ALFRED L. LEAVITT, Primary Examiner.

C. R. WILSON, Assistant Examiner.

1. THE METHOD OF PREPARING A BACK-UP ROLL TO PREVENT DAMAGE THERETO ANDADAPTED TO MATE WITH A FEMALE EMBOSSING METAL ROLL COMPRISING LAMINATINGA RESILIENT COMPOSITION BOARD TO A STEEL ROLL OF SUITABLY SMALLEROUTSIDE DIAMETER TO PRODUCE AN OVERALL DIAMETER SLIGHTLY LESS THAN THEPITCH DIAMETER OF SAID FEMALE EMBOSSING ROLL, MOISTENING SAIDCOMPOSITION BOARD WITH A SUITABLE SOLVENT, ROTAING SAID MOISTENED ROLLIN CONTACT WITH SAID FEMALE ROLL TO OBTAIN A PITCH DIAMETER OF THE MALEROLL A FEW THOUSANDTHS OF AN INCH LESS THAN THAN OF THE FEMALE ROLL,ADDING A THIN LAYER OF FLEXIBLE PLASTIC TO SAID COMPOSITION BOARD,CURING SAID PLASTIC LAYER AT A SUITABLE TEMPERATURE FOR A SUITABLE TIMETO PRODUCE A MALE BACKUP ROLL HAVING THE PITCH DIAMETER OF THE FEMALEROLL.